Nasopharyngeal carcinoma (NPC) is a major cause of cancer death in China. Its striking pattern of incidence is most likely due to several environmental factors converging in a genetically susceptible population. This work will probe the etiology of NPC on the molecular level using several genetic epidemiological approaches. The environmental factor, Epstein Barr virus (EBV) is found in all NPC biopsies. A particular strain of EBV may predominate in the endemic region. predisposing those populations to NPC. Using NPC biopsy tissue, the presence of polymorphisms within LMP-1, a key transformation-associated gene, will be correlated with NPC incidence. On the human genetic level. lesions on chromosomes 3 and 9 in NPC tumor tissue hint at the presence of tumor susceptibility loci. The boundaries and prevalence of these lesions will be determined by loss of heterozygosity (LOH) analysis at polymorphic loci, using tumor and normal tissue derived from the endemic and non- endemic areas of China. An affected sib-pair linkage analysis will also be performed to probe the mode of inheritance.